title: Radioimmunoassay for an analog of thyrotrophin-releasing hormone, gamma-butyrolactone-gamma-carbonyl-L-histidyl-L-prolinamide (DN-1417).
abstract: A heterologous radioimmunoassay method was established to determine plasma levels of gamma-butyrolactone-gamma-carbonyl-L-histidyl-L-prolinamide (DN-1417). As this compound is unstable in the incubation buffer, we introduced a conversion step. DN-1417 in the plasma was extracted with a solution of isopropanol-isobutylamine (4 : 1) and incubation was performed at room temperature for 2 h for the conversion of DN-1417 into N-[2-hydroxy-4-(isobutylcarbamoyl)butyryl]-L-histidyl-L-prolinamide (DN-isobutylamide). 125I-labeled 2-hydroxy-4-carboxybutyryl-L-histidyl-L-prolinamide and antisera, which was raised in the rabbit using an esterified derivative of DN-1417 conjugated with BSA as an antigen, were used for a sensitive radioimmunoassay of DN-isobutylamide. In this system, 0.2 ng DN-isobutylamide/ml plasma, equivalent to 0.16 ng DN-1417/ml, was detected and there was no apparent interference from its metabolites. The within-assay coefficients of variation were 7.6% at 7.73 ng/tube and 13.7% at 1.32 ng/tube. The between-assay coefficients of variation were 16.1% at 6.43 ng/tube and 12.2% at 1.20 ng/tube. The mean recovery rate of the assay system was 76.0 +/- 3.2% (S.E.M.).
mesh_terms: D000818:Animals; D003429:Cross Reactions; D007106:Immune Sera / Q000494:pharmacology; D008297:Male; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D011919:Rats, Inbred Strains; D013973:Thyrotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D007106:Immune Sera; D013973:Thyrotropin-Releasing Hormone; C035273:N-(2-hydroxy-4-(isobutylcarbamoyl)butyryl)histidylprolinamide; C035274:2-hydroxy-4-carboxybutyrylhistidylprolinamide; C029762:DN 1417